CoCoRaHS and Evapotranspiration Measurements: The other side of the water cycle

The Colorado Climate Center has been testing a low-cost instrument that was developed several years ago in Colorado that approximates the water use by grass and alfalfa. The instrument, known as an atmometer, has been used alongside a standard Class A Pan and also a complete weather station established for computing evapotranspiration (ET) from the standardized ASCE equations. Comparisons will be shown for the past three years. Preliminary results indicate this instrument may have considerable potential for helping document and track evapotranspiration in Colorado and possibly nationally.

As a result of these favorable test results, the Community Collaborative Rain, Hail and Snow network (CoCoRaHS) is now planning to incorporate ET measurements. With recent grant form the National Science Foundation and NOAA, CoCoRaHS has begun a pilot project in Colorado in 2011 to place atmometers at several locations manned by CoCoRaHS volunteers. This network may then expand to several other states in 2012-13 as we attempt to better track the two largest components of the water balance -- precipitation and evapotranspiration.. This will be a first for the network as we help to provide practical and affordable hydrologic data for the nation.